There is a severe worldwide shortage of donated organs for transplantation. Even when they are available, immune rejection is a major problem. The only widespread treatment for corneal blindness is transplantation of donor cornea, which is also in severe shortage. Corneal limbal epithelial stem cell transplantation is common but only useful when one layer is damaged. Donor corneas are still needed for deeper injuries and allogeneic grafts are still problematic and face a high rate of rejection.
Stem cell transplantation is considered the state-of-the-art and has been applied, with limited success, as a last hope treatment for restoring function to vital organs such as the heart or liver. The state-of-the-art relies on the introduction of adult source stem cells to repopulate badly damaged or diseased areas. Rejection even in the simple, immune-privileged cornea of foreign implanted stem cells is high. In the cornea transplantation using allogeneic donor tissue has remained the gold standard for over a century. Plastic-based prostheses (keratoprostheses or KPro) e.g. Boston KPro and OOKP, have been used to restore vision in severe ocular surface damage but only as last resorts, as they have an unnatural appearance, suffer from complex implantation procedures and most importantly, have serious complications including retroprosthetic membrane formation, calcification, infection, glaucoma. Continuous immunosuppression is required.
The inventors have previously successfully implanted biosynthetic implants made from (recombinant human) collagen (RHC) into 10 patients in a clinical study in Sweden. All 10 patients showed regeneration of corneal tissues and nerves, without the need of sustained immunosuppression over 4 years. We have since then strengthened the implants by introducing a second network of materials by formation of interpenetrating networks (IPNs) of recombinant human collagen and MPC-co-PEGDA (MPC=2-methacryloyloxyethyl phosphorylcholine, PEGDA=polyethylene glycol-diacrylate) (RHC-MPC). This new generation of implants have shown to be safe, and successfully promoted regeneration of corneal cells and nerves in mini-pig and rabbit models, and in two human patients. Still there is a need for an implant that remains optically clear when implanted and where the mechanical properties can be tailored in order to match the surrounding tissue and to enable suturing.